Fig. 1
From: Single ion fluorescence excited with a single mode of an UV frequency comb
Experimental setup schematic. A frequency doubled cw dye laser is used for laser cooling trapped Mg ions on the 3s 1/2−3p 3/2 transition. The same transition is interrogated with an individual mode of the UV frequency comb that derives from the third harmonic of a Ti:sapphire mode locked laser and is spatially overlapped with the cw laser. The two lasers are alternatingly turned on for 2 ms with two acousto optic modulators (AOM). Thanks to its lower power, detuning dependent residual heating/cooling due to the near resonant mode of the comb is largely suppressed (see text). The fluorescence signal is detected by spatially resolved single photon camera during the bright times of the comb i.e. the dark periods of the cooling laser. The ion trap consists of four rf-electrodes, two pairs of ring electrodes for axial confinement and four rod-like dc-electrodes (not shown) for stray field cancellation. SHG second-harmonic generation stage, SFG sum frequency generation stage, EOM electro-optical-modulator
